Rash with both clopidogrel and ticlopidine in two patients following percutaneous coronary intervention with drug-eluting stents

Update on Cilostazol: A Critical Review of Its Antithrombotic and Cardiovascular Actions and Its Clinical Applications

Cilostazol, a phosphodiesterase III inhibitor, has vasodilating and antiplatelet properties with a low rate of bleeding complications. It has been used over the past 25 years for improving intermittent claudication in patients with peripheral artery disease (PAD). Cilostazol also has demonstrated efficacy in patients undergoing percutaneous revascularization procedures for both PAD and coronary artery disease. In addition to its antithrombotic and vasodilating actions, cilostazol also inhibits vascular smooth muscle cell proliferation via phosphodiesterase III inhibition, thus mitigating restenosis. Accumulated evidence has shown that cilostazol, due to its "pleiotropic" effects, is a useful, albeit underutilized, agent for both coronary artery disease and PAD. It is also potentially useful after ischemic stroke and is an alternative in those who are allergic or intolerant to classical antithrombotic agents (eg, aspirin or clopidogrel). These issues are herein reviewed together with the pharmacology and pharmacodynamics of cilostazol. Large studies and meta-analyses are presented and evaluated. Current guidelines are also discussed, and the spectrum of cilostazol's actions and therapeutic applications are illustrated.

Intolerance to Multiple P2Y12 Inhibitors Following Percutaneous Coronary Intervention

Dual antiplatelet therapy (DAPT), defined as administration of a P2Y12 receptor inhibitor (clopidogrel, prasugrel, or ticagrelor) and aspirin, is recommended after percutaneous coronary intervention. We describe a case of a 50-year-old gentleman with intolerance to the three previously mentioned P2Y12 inhibitors following the placement of a drug-eluting stent to the left anterior descending artery. To our knowledge, based on a thorough review of the literature, this is the second case reporting a similar medical dilemma. We have discussed the multidisciplinary approach implemented to overcome this clinical challenge, which involved the use of clopidogrel with simultaneous administration of a six-day course of oral steroids.

A joint allergist/cardiologist classification for thienopyridines hypersensitivity reactions based on their symptomatic patterns and its impact on the management strategies

The role and importance of thienopyridines such as ticlopidine, clopidogrel, and prasugrel is well-established for several indications, ranging from prevention of acute coronary syndromes to percutaneous coronary interventions, where the dual antiplatelet therapy represents the gold standard to avoid denovo coronary stenosis. However, there is a significant cohort of patients with coronary artery disease who may manifest hypersensitivity reactions to thienopyridines. The examination of the various case reports from medical literature leads to identify mainly four clinical patterns of hypersensitivity to thienopyridines which involves more frequently cutaneous, hematologic, and articular tissues, therefore the kind and predominance of clinical symptoms may determine a different clinical approach to overcome or neutralize thienopyridines hypersensitivity.

Hypersensitivity reactions to modern antiplatelet and anticoagulant drugs

Anticoagulation and antiplatelet drugs are among the most commonly used medical drugs. In addition to the long-established heparins, hirudins, coumarins and antiplatelet drugs such as acetylsalicylic acid, numerous novel and predominantly synthetic pharmacologic agents have come onto the market in recent years. These new agents act at various sites in coagulation and have significantly broadened treatment options. Whilst immunological hypersensitivity reactions are on the whole rare, they have a considerable impact on patient management when they do occur. The present overview discusses the currently known hypersensitivity reactions to anticoagulant and antiplatelet agents, with particular attention to the newer substance classes including P2Y₁₂ inhibitors, glycoprotein IIb/IIIb receptor antagonists, direct factor Xa inhibitors and direct thrombin inhibitors.

Oral antiplatelet agent hypersensitivity and cross-reactivity managed by successful desensitisation

Oral platelet aggregation inhibitors are widely used for the treatment and prevention of cardiovascular diseases, including coronary stent thrombosis. Premature discontinuation following percutaneous coronary intervention would pose a grave risk of in-stent thrombosis, acute myocardial infarction and eventual death. Although they share the same mechanism of adenosine diphosphate P2Y12 platelet receptor inhibition, they belong to either the chemical class of thienopyridines (clopidogrel, prasugrel, and ticlopidine) or cyclopentyl-triazolo-pyrimidines (ticagrelor and cangrelor). This case describes the first documented cross-reactive hypersensitivity of clopidogrel towards both its fellow thienopyridine, prasugrel, as well as the structurally dissimilar ticagrelor, and its subsequent successful desensitisation.

Clopidogrel-induced spontaneous pectoral hematoma

Clopidogrel is an oral antiplatelet agent used in the treatment of coronary artery disease, peripheral vascular disease and cerebrovascular disease. Gastrointestinal symptomsincluding nausea, diarrhea and constipation are the common side effects ofthis drug. Serious side effects like intracranial hemorrhage and severe neutropenia were also reported but spontaneous pectoral hematoma due to the clopidogrel has not been reported previously. We present a case of large spontaneous pectoral hematoma during clopidogrel therapy in an elderly woman.

Clopidogrel-induced neutropenia after coronary stenting: is cilostazol a good alternative?

Dual antiplatelet therapy with aspirin plus thienopyridines has become the standard treatment of patients undergoing coronary stenting. Clopidogrel has mostly replaced the use of ticlopidine due to its more favourable adverse event profile. However, also the use of clopidogrel is not without side effects. Clopidogrel major adverse events are represented by marrow suppression, manifesting with aplastic anaemia, thrombocytopenia and neutropenia. When clopidogrel toxicity occurs, there are few and unsubstantiated alternative treatments and thus, in these cases, medical decisions may be very difficult. We report a case of clopidogrel-induced bone marrow toxicity manifesting with severe neutropenia in a patient treated with multiple coronary stents and provide suggestions for an alternative treatment.

Recurrent acute stent thrombosis due to allergic reaction secondary to clopidogrel therapy

Despite significant benefits including mortality advantage demonstrated with antiplatelet therapy in large clinical trials, the occurrence of adverse ischemic events, including stent thrombosis after percutaneous coronary intervention has been the challenging and devastating complication. Clopidogrel as a monotherapy, or more common in combination with aspirin, represents a cornerstone of modern pharmacotherapy in the invasive era. Although vigilance in maintenance of this dual antiplatelet treatment is mandatory, obligatory cessation of one of these agents can be observed in rare circumstances of adverse events. We describe a patient who developed recurrent acute stent thrombosis associated with clopidogrel-induced allergic reaction and discuss our therapeutic considerations.

Allergic reactions to clopidogrel and cross-reactivity to other agents

Clopidogrel is a widely used antiplatelet agent, particularly after coronary stent implantation. About 1% of patients have allergic or hematologic adverse reactions to clopidogrel. This has important therapeutic implications, as premature discontinuation of clopidogrel is the strongest risk factor for stent thrombosis. Clopidogrel allergy most commonly manifests as a rash. It is important to distinguish this from other causes of rash occurring in patients who have had a recent coronary stent. Although antihistamines and short-term oral corticosteroids are effective in treating most clopidogrel hypersensitivity reactions, some persistent reactions may require discontinuation of clopidogrel. When discontinuation of clopidogrel is required, substitution with an alternative thienopyridine such as ticlopidine traditionally has been performed. However, a recent study suggests that there may be as high as a 27% risk of recurrence of non-life-threatening allergic reactions in such patients, which are usually similar to the allergic reactions that occurred with clopidogrel. No data are available regarding the frequency of cross-reactivity to prasugrel and ticagrelor; these may be potential therapeutic options in some patients.

Inhibition of vascular ectonucleotidase activities by the pro-drugs ticlopidine and clopidogrel favours platelet aggregation

BACKGROUND AND PURPOSE

After conversion to their active forms by the liver, ticlopidine and clopidogrel exert antiplatelet effects through irreversible inhibition of the P2Y₁₂ receptor. Concentrations of nucleotides such as ADP, the physiological agonist at platelet P2Y₁ and P2Y₁₂ receptors, are regulated by vascular ectonucleotidases, mainly nucleoside triphosphate diphosphohydrolase (NTPDase)1 and ecto-5'-nucleotidase. Here we evaluate the effect of these pro-drugs on vascular ectonucleotidase activity and on the natural function of these enzymes in regulating platelet aggregation.

EXPERIMENTAL APPROACH

Nucleotidase assays were performed by HPLC and by P(i) determination, using human umbilical vein endothelial cells (HUVEC) and protein extracts from transfected COS-7 cells as sources of enzymes. Platelet aggregation was assayed using human platelet-rich plasma.

KEY RESULTS

Each pro-drug inhibited endothelial ectonucleotidase activities and decreased their ability to block platelet aggregation in vitro. At their therapeutic concentrations, ticlopidine (60 µM) and clopidogrel (20 µM) inhibited ADP hydrolysis by HUVEC by about 80%, and AMP hydrolysis by one-third. Accordingly, these compounds showed a mixed-type inhibition of recombinant human NTPDase1 with an apparent K(i) (K(i,app) ) of 10 µM (clopidogrel) and 14 µM (ticlopidine). Recombinant rat ecto-5'-nucleotidase, but not its human orthologue, was inhibited by ticlopidine with a K(i,app) of 4.5 mM.

CONCLUSIONS AND IMPLICATIONS

These pro-drugs facilitated platelet aggregation via the inhibition of vascular NTPDase1 in vitro. Further studies should be performed to assess whether this effect also occurs in vivo, especially at the beginning of treatment, before sufficient levels of active metabolites are produced by the liver.

A novel, accelerated method of desensitization in a patient with a documented hypersensitivity reaction to clopidogrel

Current standard of care following a percutaneous coronary intervention with stent placement necessitates the use of dual anti-platelet therapy with aspirin and commonly clopidogrel. There is a subset of patients who have a significant clopidogrel allergy and life-threatening hypersensitivity reactions. Desensitization is the process of inducing tolerance to a sensitizing agent via repeated exposure to the agent. There have been previously reported protocols for clopidogrel desensitization. These protocols differ in length and dose escalation and a universally accepted clopidogrel desensitization protocol has yet to be established. We discuss here a novel accelerated approach to clopidogrel desensitization in a patient with a documented hypersensitivity reaction.

Clopidogrel Hypersensitivity: A Novel Multi-Day Outpatient Oral Desensitization Regimen

BACKGROUND

Clopidogrel hypersensitivity has posed a problem for the acute treatment and long-term care of a particular patient population with coronary artery disease and stent placement. Patients with clopidogrel hypersensitivity have had an increased risk of hypersensitivity reactions, including anaphylaxis, if they ingest clopidogrel without undergoing an oral desensitization procedure. The previously published desensitization protocols have either been performed in the intensive care unit, requiring significant cost and healthcare utilization, or have required a full-day outpatient commitment on behalf of the patient.

OBJECTIVE

To determine whether a multi-day outpatient oral clopidogrel desensitization protocol is effective and safe for patients with clopidogrel hypersensitivity.

METHODS

gWe retrospectively assessed the efficacy of a 10-dose outpatient multiday clopidogrel desensitization protocol performed in a university allergy-immunology center from April 2006 to October 2008 in patients with clopidogrel hypersensitivity. Patients were desensitized over 2–3 half-day clinical visits and were able to go home between desensitization sessions. A preliminary cost analysis was performed using the average of actual costs for the outpatient clopidogrel desensitization procedure and was compared with the average cost for an inpatient oral desensitization completed at our institution.

RESULTS

Eight patients with coronary artery disease, cardiac stent placement, and clopidogrel hypersensitivity underwent an outpatient multi-day oral clopidogrel desensitization procedure. All patients were successfully desensitized with the multi-day protocol without complications. No patient had recurrence of allergic reaction 3 months after the procedure. A preliminary cost analysis demonstrated a lower cost for the outpatient compared to the inpatient oral clopidogrel desensitization protocol.

CONCLUSIONS

This outpatient 10-dose multi-day clopidogrel desensitization protocol is a safe and effective novel approach for the treatment of clopidogrel hypersensitivity in patients with coronary artery disease and cardiac stent placement. In addition to safety and efficacy, this protocol offers the patient the convenience of avoiding hospital admission or full-day time commitments.